68 lines
4.3 KiB
HTML
68 lines
4.3 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Threads considerations" />
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<meta name="abstract" content="A UDF, defined as FENCED, runs in the same job as the SQL statement that called it. However, the UDF runs in a system thread, separate from the thread that is running the SQL statement." />
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<meta name="description" content="A UDF, defined as FENCED, runs in the same job as the SQL statement that called it. However, the UDF runs in a system thread, separate from the thread that is running the SQL statement." />
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<meta name="DC.subject" content="UDFs (User-defined functions), thread considerations" />
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<meta name="keywords" content="UDFs (User-defined functions), thread considerations" />
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<meta name="DC.Relation" scheme="URI" content="rbafywudfextern.htm" />
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<meta name="DC.Relation" scheme="URI" content="../rzahw/rzahwovepo.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbafysqlpfenced.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="rbafyudfthreads" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Threads considerations</title>
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</head>
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<body id="rbafyudfthreads"><a name="rbafyudfthreads"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Threads considerations</h1>
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<div><p>A UDF, defined as FENCED, runs in the same job as the SQL statement
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that called it. However, the UDF runs in a system thread, separate from the
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thread that is running the SQL statement.</p>
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<div class="section"></div>
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<div class="section"><p>Because the UDF runs in the same job as the SQL statement, it
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shares much of the same environment as the SQL statement. However, because
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it runs under a separate thread, the following threads considerations apply: </p>
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<ul><li>The UDF will conflict with thread level resources held by the SQL statement's
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thread. Primarily, these are the table resources discussed above. </li>
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<li>UDFs do not inherit any program adopted authority that may have been active
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at the time the SQL statement was called. UDF authority comes from either
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the authority associated with the UDF program itself or the authority of the
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user running the SQL statement. </li>
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<li>The UDF cannot perform any operation that is blocked from being run in
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a secondary thread. </li>
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<li>The UDF program must be created such that it either runs under a named
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activation group or in the activation group of its caller (ACTGRP parameter).
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Programs that specify ACTGRP(*NEW) will not be allowed to run as UDFs.</li>
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</ul>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbafywudfextern.htm" title="You can write the executable code of a UDF in a language other than SQL.">Write UDFs as external functions</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="rbafysqlpfenced.htm" title="When creating a user-defined function (UDF) consider whether to make the UDF an unfenced UDF.">Fenced or unfenced considerations</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../rzahw/rzahwovepo.htm">Database considerations for multithreaded programming</a></div>
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</div>
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</div>
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</body>
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</html>
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